Several methods for treating diseased tissues using thermal therapy are in use. Thermal therapy involves application of thermal energy (heat) to a diseased region or organ. The proper application of heat can eliminate or reduce the disease by killing diseased cells in the organ. Cancer cells can be treated by the application of a proper amount of heat or by heating to a certain temperature. Thermal therapy has been applied to the treatment of prostate cancer, but other diseased organs and tissues may similarly be treated. The modality for applying the thermal treatment may vary, and the art teaches the use of RF electromagnetic energy, laser and ultrasound energy for heating a target region. Some prostate thermal treatments are externally delivered by an energy delivery device outside the general volume of the prostate or even outside of the body of the patient, e.g., focused ultrasound surgery. Other prostate thermal treatments are internally delivered from within the general volume of the prostate, e.g., using transurethral energy sources delivering energy from within the urethra outwardly into the surrounding volume of the prostate.
FIG. 1 illustrates a general arrangement of a male patient in cross section 10. Existing thermal therapy treatment procedures can vary, but in a class of treatments the patient may lie supine as shown and the prostate 100 is subjected to thermal heating from a therapy applicator source, which can be a laser, RF antenna, ultrasound transducer or other source. The prostate 100 generally surrounds the urethra. Therefore, a class of treatments inserts a narrow applicator (not shown) into the urethra 120 of the patient and guides the active portion of the applicator until it is substantially surrounded by the prostate 100. This type of treatment is called transurethral because it delivers energy into the prostate 100 from within the urethra 120.
An unwanted side effect of the heating of the diseased tissue can be the over-heating of adjacent non-diseased tissue and organs. This is because the heating effects of the thermal therapy procedure have a finite spatial distribution that makes it difficult or impossible to fully heat the target zone while not heating the surrounding volumes at all. Also, the living body causes heat conduction and perfusion to spread the thermal therapy heat to volumes in the vicinity of the intended target volume. Specifically, as an example, in the thermal therapy of the prostate, the rectum 110 and other healthy tissues near the prostate 100 can be heated beyond what is safe or healthy for the patient. It is desired to limit the thermal dose or maximum temperature applied to these tissues, e.g., to the rectum wall 112 proximal to the prostate 120. The term “proximal” is used herein as commonly used in patent specifications to denote things that are adjacent to or near one another.
Some existing protocols employ cooling methods and devices to keep the temperature rise in healthy tissues around the target volume to within a safe limit. These protocols, e.g., US Pub. No. 2011/0319748 A1, disclose a heat exchange apparatus that is placed into a body cavity (e.g., the rectum through orifice 130) and that receives a temperature-controlled cooling fluid (e.g., water) to cool the rectum during the thermal therapy of the prostate 100. The present application is directed to a mechanically and thermally optimized cooling device for cooling the rectum 110 and its walls 112 during thermal therapy procedures in its vicinity, including during thermal therapy to the prostate 100.